This invention relates to a method for the recovery of mineral values from mineral ores by froth flotation.
Flotation is a process of treating a mixture of finely divided mineral solids, e.g., a pulverulent ore, suspended in a liquid whereby a portion of the solids is separated from other finely divided mineral solids, e.g., clays and other like materials present in the ore, by introducing a gas (or providing a gas in situ) in the liquid to produce a frothy mass containing certain of the solids on the top of the liquid, and leaving suspended (unfrothed) other solid components of the ore. Flotation is based on the principle that introducing a gas into a liquid containing solid particles of different materials suspended therein causes adherence of some gas to certain suspended solids and not to others and makes the particles having the gas thus adhered thereto lighter than the liquid. Accordingly, these particles rise to the top of the liquid to form a froth.
Various flotation agents have been admixed with the suspension to improve the frothing process. Such added agents are classed according to the function to be performed and include collectors such as xanthates, thionocarbamates and the like; frothers which impart the property of forming a stable froth, e.g., natural oils such as pine oil and eucalyptus oil; modifiers such as activators to induce flotation in the presence of a collector, e.g., copper sulfate; depressants, e.g., sodium cyanide, which tend to prevent a collector from functioning as such on a mineral which it is desired to retain in the liquid, and thereby discourage a substance from being carried up and forming a part of the froth; pH regulators to produce optimum metallurgical results, e.g., lime and soda ash; and the like. The specific additives used in a flotation operation are selected according to the nature of the ore, the mineral sought to be recovered and the other additives which are to be used in combination therewith.
Flotation is employed in a number of mineral separation processes including the selective separation of sulfide and oxide minerals containing metals such as copper, zinc, lead, nickel, molybdenum and the like.
Collectors commonly used for the recovery of metal containing minerals include xanthates, dithiophosphates, and thionocarbamates. Such collectors are widely used in various flotation processes in which metal-containing sulfide minerals are recovered. However, improvements in the recovery rate and/or selectivity of the collectors towards mineral values over the gangue, i.e., the undesired portions of the mineral ore, are always desired. In addition, these collectors do not provide commercially acceptable recovery of metal-containing oxide minerals and of certain metal-containing sulfide minerals such as precious metal-containing sulfide minerals (e.g., gold-containing sulfide minerals).
Of the other collectors, the mercaptan collectors are very slow kinetically in the flotation of metal-containing sulfide mineral and have an offensive odor. The disulfides and polysulfides give relatively low recoveries with slow kinetics. Therefore, the mercaptans, disulfides and polysulfides are not generally used commercially.
In view of the foregoing, a method for froth flotation which is useful in the recovery, at relatively good recovery rates and selectivities towards the mineral values over the gangue, of a broad range of metal values from metal ores, including the recovery of metal-containing sulfide minerals, sulfidized metal-containing oxide minerals and metal-containing oxide minerals, is desired.